Pi-eyed

Today is pi day, a celebration of one of the most-used yet bizarrest numbers in all of mathematics,
writes Alok Jha.
Pi (which begins 3.14, hence the celebration today) represents the ratio of a circle's circumference to its diameter. It goes on forever, and there are no patterns in the order of the digits. Little wonder mathematicians call it an
irrational number. It has its uses in countless physics equations, endless mathematical formulae and near-infinite engineering problems.

A calculator, as not used by planet-brain mathematicians working out pi to billions of decimal pointsToday is pi day, a celebration of one of the most-used yet bizarrest numbers in all of mathematics, writes Alok Jha.

Pi (which begins 3.14, hence the celebration today) represents the ratio of a circle's circumference to its diameter. It goes on forever, and there are no patterns in the order of the digits. Little wonder mathematicians call it an irrational number. It has its uses in countless physics equations, endless mathematical formulae and near-infinite engineering problems.

Before this starts sounding like a maths lesson, we should point out that the number is rooted in plenty of popular culture. Kate Bush sang the first 137 digits in a song, titled π, on her recent album, Aerial (although some people accuse her of getting the numbers wrong); Carl Sagan wrote about the possibility of findig a fingerprint of God in a version of pi; and Professor Frink (of The Simpsons fame) shouts "pi is exactly 3" to get the attention of a bunch of scientists.

Pi day (incidentally, the same day as Albert Einstein's birthday) is celebrated by mathematicians around the world by considering the rold the number plays in our lives. That or eating pies, playing piñata, drinking piña colada, eating pineapple or watching the film Pi.

There are lots of ways to remember pi, incuding things called piems, poems where the length of each word represents a digit. There is even a field of study called piphilology which uses mnemonics to remember the digits of pi.

You can search for your own favourite string of numbers (what do you mean you don't have a favourite string of numbers? Try your birthday) in the first 3.2bn digits of pi.

If pi day has has piqued your interest in the number, you might want to stick a note in the diary for the next celebration: pi approximation day on July 22, in honour of 22/7, the most popular fraction used to represent pi in calculations.